Op-Ed: More on filtered permeability, from the USA

Steve Tracy from Davis CA, USA writes:

Your earlier piece on filtered permeability — On Filtered Permeability as a sustainability tool, World Streets, 20 Oct. 2011 — sure got my attention. I spent three hours at the Davis City Council meeting Tuesday evening last week arguing on behalf of residents and the advocacy group Davis Bicycles! for traffic calming in our neighborhood, which is plagued by cut-through traffic. (Though I like your term “rat running” better.)

Platted in 1912, Old North Davis is viewed as the first suburb of Davis, being just 1,500 feet from our train station, which is at the very center of the rail hub that is the reason the town is here. Though legend has it the developers were warned they would go bust because their development was “too far out of town.”

The images show that Old North Davis was laid out 99 years ago as a continuation of the traditional grid pattern of the older downtown core of Davis. You can see on the second image that grid begins to decay (devolve?) with post-war developments to the north, east, and west of our neighborhood. Developments at the edge of Davis are characterized by cul-de-sacs dumping traffic onto the poorly connected looping curve collector streets.

Standing before the City Council, I argued that allowing traffic to filter through the grid distributes the traffic load better. I said our residents are willing to share our streets, but only ask for some traffic calming to help drivers behave. I didn’t point out that the north/south street at the west edge of our district is an arterial. Another north/south arterial with a high traffic load is the second street over from our eastern boundary that cuts through a solid residential area with around 50 homes and back units in just two blocks

I have long been a fan of the grid’s ability to distribute traffic more evenly through the system. But that post last week caused me to get up from the computer to sit on the couch and pout. And ponder a more aggressive approach. My hypocrisy is that since I returned from a research trip to Europe a year ago, I have been showing slides and touting the cut-through opportunities many European cities provide for cyclists and pedestrians but restrict vehicles from using.

I also think all the wonderful counter-flow bike lanes we see on one-way streets in Europe fall into this class. We enjoyed riding a shared bike on a counter-flow bike lane in Vienna. Motor vehicles cannot use this short cut in this direction, which in a couple of minutes took us the 1,000 feet (300 meters) from Augustinerplatz (behind the camera) to Michaelerplatz,. I can’t imagine the circuitous route a vehicle driver would have to take to connect these spots in the direction we went, but 10 minutes is a good guess of the time required.

We were successful arguing our case before the City Council, which approved a modest amount of funding to do some traffic calming design work and preliminary cost estimates in the neighborhoods near downtown affected by rat running. Our neighborhood association held a meeting two nights later to go over maps and talk issues and traffic patterns. We considered the two different philosophical approaches to traffic calming, which I might call barricades vs behavior.

The barricade approach favors bollards, curb extensions that block one lane, and turning restrictions. The nearby cities of Berkeley and Sacramento have pursued this approach. Barricading certainly cuts down on rat running, but it also inconveniences residents and forces them to travel longer distances to get to and from their homes by car.

The behavior approach keeps all possible routes open to all users of the street, but forces drivers to slow down and behave responsibly by the use of chicanes, neighborhood traffic circles, narrow vehicle lanes, and as a last resort speed bumps or tables.

I guess the simplest way to put it is filtered permeability with a porous filter adjusted to allow some drivers through. Drivers willing to travel at speeds appropriate for safe sharing of the streets with pedestrians, bicyclists, and local residents will think this is fine and go through the filter. Just as cyclists are allowed to ride in the pedestrian district in the earlier photographs, but only at an appropriate speed. Those drivers too impatient to accept the time they lose by the lower speeds the traffic calming measures will impose on them will stick to the arterials.

Back to pouting on the couch, where I thought of two filters I use frequently. One was in the kitchen sink last night, draining the spaghetti we had just cooked. Big holes in it to let the water out but hold the pasta back. That is like our neighborhood is now with streets open to rat running, impeded only by a few stop signs here and there.

Another filter we use purifies water for drinking on our backpacking trips into wilderness areas in California and Utah. This one can convert frog-scum to life-saving nectar with holes so small some molecules cannot get through. Applied to the streets, this filter would let bicyclists, pedestrians, local residents in cars, and well-behaved rat-runners through.

Two filters, very different in permeability.

At our neighborhood meeting, residents came down strongly in favor of gentle filtering and rejected the barricading approach. Think of it as the drinking water filter. This decision was primarily for the personal inconvenience we would all suffer with barricades, but also because some of our residents live on the arterials I mentioned earlier that would no doubt see heavier traffic volumes.

All that said, even if our residents pushed for it, I don’t think we can win the barricade battle at City Hall in Davis. So we’ll take the initial steps of traffic calming we just got design funding for, after a six-year effort. Then we will work with the consultant designers to make sure the features we choose are flexible enough to convert to full vehicle restrictions in the future if that’s what we want.

Just to make a point for the purposes of discussion, I also show these last two images taken at the same intersection as a great example of how European designers are providing separate but equal environments for the many users of the street. In this example from Freiburg you see tramway, pedestrian, bicycle, and vehicle spaces on a HUGE intersection all clearly marked and for the most part respected by all. A post-war intersection, to be sure.

# # #

Full disclosure: I may be the worst car fanatic that reads World Streets on a regular basis. I have loved cars my whole life, and learned to drive at ten on a beach in Mexico. Even worse, I love racing. I raced off-road in the California desert at 14. I regularly work on a pit crew for friends who run at vintage racing events in California (you Europeans call these “Old Timers”). They took me to France to wash windshields at the Le Mans Classic a few years ago. I love driving the right car on the right road outside of towns. But I have never been inside a town I wouldn’t rather explore on foot or on a bike.

What I’m trying to say is that at this point in my life if a lead-foot sinner like me can work so hard to tip the balance away from carbon-heavy transportation in cities, anyone should be able to embrace it. Our role at this crisis point in history must be to become the best possible stewards of this precious planet, for those who are not yet born and cannot enter the debate. The great-great-grandchildren you may never see will love you for it. Heal the planet. Get healthy yourself in the process. Get on your bike!

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